Topics of current studies include 1) cloning of mitochondrial DNA sequences of Crytococcus neoformans; 2) isolation of antigenic variants of Candida albicans; 3) determination of ploidy and karyotype of Candida stellatoidea; 4) comparison of Cladosporium trichoides, an etiologic agent of mycotic brain abscess, with Xylohypha nigrescens. In current studies, we have determined that the mitochondrial genome size of the two varieties of Crytococcus neoformans range between 40-45 kilobases. Some cloned mt DNA fragments ranging between 1 to 1.8 kb showed variety specific patterns of homology when they were hybridized with total DNA digests of numerous isolates obtained from various parts of the world. These findings support the previous results that the phenotypic differences between the two varieties are based on their genetic differences. A method, without mutagenesis, was developed to isolate antigenic variants from serotype A as well as B isolates of Candida albicans.